The line is absolutely not clear.
Is ABC allowed to run commercials for its own shows?
ABC is owned by Disney. Is ABC allowed to run commercials for Disney shows? Is it allowed to run commericals for Disney toys?
Can ABC run commercials for Bounty paper towels, in exchange for Bounty putting ads for ABC shows on its paper towel packaging?
Literally no money is being exchanged so far.
I'm familiar with a lot of gray areas that courts regularly have to decide on. But trying to distinguish advertising from free speech sounds like the most difficult free speech question I've ever come across. People are allowed to express positive opinions about products, and even try to convince their friends, that's free speech. Trying to come up with a global definition of advertising that doesn't veer into censorship... I can't even imagine. Are you suddenly prevented from blogging about a water bottle you like, because you received a coupon for a future water bottle? Because if you use that coupon, it's effectively money exchanged. What if your blog says you wouldn't have bothered writing about the bottle, but you were so impressed with the coupon on top of everything else it got you to write?
You can argue over any of these examples, but that's the point: you're arguing, because the line isn't clear.